/*
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at 
 * 
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *  
 */

using System;
using java = biz.ritter.javapi;
using org.apache.commons.collections;

namespace org.apache.commons.collections.iterators
{

    /**
     * Implements a {@link ListIterator} over an array. 
     * <p>
     * The array can be either an array of object or of primitives. If you know 
     * that you have an object array, the {@link ObjectArrayListIterator}
     * class is a better choice, as it will perform better.
     * 
     * <p>
     * This iterator does not support {@link #add(Object)} or {@link #remove()}, as the array 
     * cannot be changed in size. The {@link #set(Object)} method is supported however.
     *
     * @see org.apache.commons.collections.iterators.ArrayIterator
     * @see java.util.Iterator
     * @see java.util.ListIterator
     *
     * @since Commons Collections 3.0
     * @version $Revision$ $Date$
     *
     * @author Neil O'Toole
     * @author Stephen Colebourne
     * @author Phil Steitz
     */
    public class ArrayListIterator : ArrayIterator
            , java.util.ListIterator<Object>, ResettableListIterator
    {

        /**
         * Holds the index of the last item returned by a call to <code>next()</code>
         * or <code>previous()</code>. This is set to <code>-1</code> if neither method
         * has yet been invoked. <code>lastItemIndex</code> is used to to implement 
         * the {@link #set} method.
         *
         */
        protected int lastItemIndex = -1;

        // Constructors
        // ----------------------------------------------------------------------
        /**
         * Constructor for use with <code>setArray</code>.
         * <p>
         * Using this constructor, the iterator is equivalent to an empty iterator
         * until {@link #setArray(Object)} is  called to establish the array to iterate over.
         */
        public ArrayListIterator()
            : base()
        {
        }

        /**
         * Constructs an ArrayListIterator that will iterate over the values in the
         * specified array.
         *
         * @param array the array to iterate over
         * @throws IllegalArgumentException if <code>array</code> is not an array.
         * @throws NullPointerException if <code>array</code> is <code>null</code>
         */
        public ArrayListIterator(Object array)
            : base(array)
        {
        }

        /**
         * Constructs an ArrayListIterator that will iterate over the values in the
         * specified array from a specific start index.
         *
         * @param array  the array to iterate over
         * @param startIndex  the index to start iterating at
         * @throws IllegalArgumentException if <code>array</code> is not an array.
         * @throws NullPointerException if <code>array</code> is <code>null</code>
         * @throws IndexOutOfBoundsException if the start index is out of bounds
         */
        public ArrayListIterator(Object array, int startIndex)
            : base(array, startIndex)
        {
            this.startIndex = startIndex;
        }

        /**
         * Construct an ArrayListIterator that will iterate over a range of values 
         * in the specified array.
         *
         * @param array  the array to iterate over
         * @param startIndex  the index to start iterating at
         * @param endIndex  the index (exclusive) to finish iterating at
         * @throws IllegalArgumentException if <code>array</code> is not an array.
         * @throws IndexOutOfBoundsException if the start or end index is out of bounds
         * @throws IllegalArgumentException if end index is before the start
         * @throws NullPointerException if <code>array</code> is <code>null</code>
         */
        public ArrayListIterator(Object array, int startIndex, int endIndex)
            : base(array, startIndex, endIndex)
        {
            this.startIndex = startIndex;
        }

        // ListIterator interface
        //-----------------------------------------------------------------------
        /**
         * Returns true if there are previous elements to return from the array.
         *
         * @return true if there is a previous element to return
         */
        public virtual bool hasPrevious()
        {
            return (this.index > this.startIndex);
        }

        /**
         * Gets the previous element from the array.
         * 
         * @return the previous element
         * @throws NoSuchElementException if there is no previous element
         */
        public virtual Object previous()
        {
            if (hasPrevious() == false)
            {
                throw new java.util.NoSuchElementException();
            }
            this.lastItemIndex = --this.index;
            return java.lang.reflect.Array.get(this.array, this.index);
        }

        /**
         * Gets the next element from the array.
         * 
         * @return the next element
         * @throws NoSuchElementException if there is no next element
         */
        public override Object next()
        {
            if (hasNext() == false)
            {
                throw new java.util.NoSuchElementException();
            }
            this.lastItemIndex = this.index;
            return java.lang.reflect.Array.get(this.array, this.index++);
        }

        /**
         * Gets the next index to be retrieved.
         * 
         * @return the index of the item to be retrieved next
         */
        public virtual int nextIndex()
        {
            return this.index - this.startIndex;
        }

        /**
         * Gets the index of the item to be retrieved if {@link #previous()} is called.
         * 
         * @return the index of the item to be retrieved next
         */
        public virtual int previousIndex()
        {
            return this.index - this.startIndex - 1;
        }

        /**
         * This iterator does not support modification of its backing collection, and so will
         * always throw an {@link UnsupportedOperationException} when this method is invoked.
         *
         * @throws UnsupportedOperationException always thrown.
         * @see java.util.ListIterator#set
         */
        public virtual void add(Object o)
        {
            throw new java.lang.UnsupportedOperationException("add() method is not supported");
        }

        /**
         * Sets the element under the cursor.
         * <p>
         * This method sets the element that was returned by the last call 
         * to {@link #next()} of {@link #previous()}. 
         * <p>
         * <b>Note:</b> {@link ListIterator} implementations that support
         * <code>add()</code> and <code>remove()</code> only allow <code>set()</code> to be called
         * once per call to <code>next()</code> or <code>previous</code> (see the {@link ListIterator}
         * javadoc for more details). Since this implementation does
         * not support <code>add()</code> or <code>remove()</code>, <code>set()</code> may be
         * called as often as desired.
         *
         * @see java.util.ListIterator#set
         */
        public virtual void set(Object o)
        {
            if (this.lastItemIndex == -1)
            {
                throw new java.lang.IllegalStateException("must call next() or previous() before a call to set()");
            }

            java.lang.reflect.Array.set(this.array, this.lastItemIndex, o);
        }

        /**
         * Resets the iterator back to the start index.
         */
        public override void reset()
        {
            base.reset();
            this.lastItemIndex = -1;
        }

    }
}